480 De sulphur ation of Metals . 
my knowledge were made at a temperature a little raised, I pro- 
ceeded in the following manner : I put into a crucible, pyrites of 
iron pulverized : covered it with charcoal in powder, and heated it 
in the forge for an hour ; I found a mass still preserving all the 
characters of pyrites : it seemed to have been completely melted, 
and retained two thirds of the sulphur contained in the natural py- 
rites. This experiment being repeated, left me in no uncertainty 
upon the effects of heat by itself, upon sulphuret of iron, and I 
thought I might conclude, that, whatever be the temperature, 
these effects produce a partial decomposition. 
Sulphuretted copper and pyritous copper, submitted to the ac- 
tion of heat, produce effects analogous to those observed with res- 
pect to iron : the distillation of the pyritous copper furnished but 
very little sulphur : these two kinds of minerals of copper may in 
short be considered as mixtures of the sulphurets of copper and 
of iron, and the sulphur which heat separates from it, proceeds al- 
most entirely from the sulphuret of iron. 
The sulphuret of lead, or galena, is one of those minerals the 
treatment of which was most various : all chemists agree in re- 
garding it as composed of sulphur and lead only, in the proportion 
of 15 of the former, and 85 of the latter. I was the more careful 
in observing the effects of caloric upon the galena, because, by 
trying to separate the sulphur from it by this agent, I expected to 
obtain lead in a metallic state, the weight and fusibility of which 
render the re-union very easy. It was, besides, very easy for me 
to operate without the contact of atmospheric air, 
I put into a retort 30 grammes of galena reduced to powder, 
which I heated for two hours, but not so strongly as to make it ag- 
glutinate : a very little sulphuric acid only was disengaged, pro- 
duced by the action of the air of the vessels, and I perceived no 
sulphur sublimed at the neck of the retort. I increased the fire 
for about two hours more, until the galena and the vessel which 
contained had undergone a kind of fusion. The sulphur volatilized 
in this second part of the operation was in so small a quantity that 
it was not possible for me to detach and weigh it : the residue was 
of a metallic lustre ; it was agglutinated, and did not contain an 
atom of ductile lead*. 
* There are few chemists who have not made this experiment with similar 
results. I may here remark, that if the heat had been long enough continued* 
and in the open air, the galena would have been completely roasted. 
